1. Field of the Invention
The present invention relates to an imaging device and a focusing control method.
2. Description of the Related Art
In recent years, according to the increase in resolution of an imaging element such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor, demand for information devices having an imaging function, such as a digital still camera, a digital video camera, a mobile phone such as a smart phone, or a personal digital assistant (PDA) has rapidly increased. Such an information device having an imaging function is referred to as an imaging device.
In such an imaging device, as a focusing control method for focusing on a main subject, a contrast auto-focus (AF) method or a phase difference AF method (for example, WO2013-047160A and JP2010-152161A) is employed. Since the contrast AF method and the phase difference AF method have respective advantages, an imaging device that uses both of the advantages has also been proposed (for example, JP2010-139942A and JP2010-204294A).
It is known that in a case where a focusing control based on the phase difference AF method is performed using an imaging element in which phase difference detection pixels are discretely arranged in an imaging surface, in a case where a high frequency part is present in a captured subject image, the reliability of the focusing control is reduced. Thus, in JP2010-204294A, it is determined whether a periodic pattern is present in a subject from frequency analysis of imaging pixels, and in a case where a periodic pattern is present, the focusing control based on a contrast AF method instead of the phase difference AF method is performed.